Field of the Invention
This invention is directed to pyridazine-3-carboxamide compounds which act as inhibitors of Janus kinases (JAKs). This invention is also directed to pharmaceutical compositions containing the pyridazine-3-carboxamide compounds and methods of using the compounds or compositions for the treatment of conditions in which modulation of the JAK pathway or inhibition of JAK kinases are therapeutically relevant such as inflammatory, autoimmune disorders, as well as cancer. The diseases or conditions involving inflammation or immune responses, such as rheumatoid arthritis, psoriasis, Crohn's disease, asthma, rhinitis, inflammatory bowel disease, colitis, transplant rejection, etc. The invention is also directed to methods of making the compounds described herein.
State of the Art
Protein kinases constitute a large family of structurally related enzymes that are responsible for the control of a variety of signal transduction processes within cells (see, e.g., Hardie and Hanks, The Protein Kinase Facts Book, I and II, Academic Press, San Diego, Calif., 1995). Protein kinases are thought to have evolved from a common ancestral gene due to the conservation of their structure and catalytic function. Almost all kinases contain a similar 250-300 amino acid catalytic domain. The kinases can be categorized into families by the substrates they phosphorylate (e.g., protein-tyrosine, protein-serine/threonine, lipids, etc.). Sequence motifs have been identified that generally correspond to each of these families (see, e.g., Hanks & Hunter, (1995), FASEB J. 9:576-596; Knighton et al., (1991), Science 253:407-414; Hiles et al., (1992), Cell 70:419-429; Kunz et al., (1993), Cell 73:585-596; Garcia-Bustos et al., (1994), EMBO J. 13:2352-2361).
Many diseases are associated with abnormal cellular responses triggered by protein kinase-mediated events. These diseases include autoimmune diseases, inflammatory diseases, bone diseases, metabolic diseases, neurological and neurodegenerative diseases, cancer, cardiovascular diseases, allergies, asthma, Alzheimer's disease and hormone-related diseases. As a consequence, there have been substantial efforts in medicinal chemistry to find inhibitors of protein kinases for use as therapeutic agents.
Janus kinases (or JAKs) are a family of cytoplasmic protein tyrosine kinases including JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2). The JAKs play a crucial role in cytokine-dependent regulation of proliferation and function of cells involved in immune response. Each of the JAK kinases is selective for the receptors of certain cytokines, though multiple JAK kinases can be affected by particular cytokine or signaling pathways. Studies suggest that JAK3 associates with the common cytokine receptor gamma chain (Fcγ or γc) of the various cytokine receptors. JAK3 in particular selectively binds to receptors and is part of the cytokine signaling pathway for and activated by IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21. JAK1 interacts with, among others, the receptors for cytokines IL-2, IL-4, IL-7, IL-9 and IL-21, while JAK2 interacts with, among others, the receptors for IL-9 and TNF-α. Upon the binding of certain cytokines to their receptors (e.g., IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21), receptor oligomerization occurs, resulting in the cytoplasmic tails of associated JAK kinases being brought into proximity and facilitating the trans-phosphorylation of tyrosine residues on the JAK kinase. This trans-phosphorylation results in the activation of the JAK kinase.
The downstream substrates of JAK family kinases include the signal transducer activator of transcription (STAT) proteins. Phosphorylated JAK kinases bind various STAT (Signal Transducer and Activator of Transcription) proteins. STAT proteins, which are DNA binding proteins activated by phosphorylation of tyrosine residues, function both as signaling molecules and transcription factors and ultimately bind to specific DNA sequences present in the promoters of cytokine-responsive genes (Leonard et al., (2000), J. Allergy Clin. Immunol. 105:877-888).
JAK/STAT signaling has been implicated in the mediation of many abnormal immune responses such as allergies, asthma, autoimmune diseases such as transplant (allograft) rejection, rheumatoid arthritis, amyotrophic lateral sclerosis and multiple sclerosis, as well as in solid and hematologic malignancies such as leukemia and lymphomas. For a review of the pharmaceutical intervention of the JAK/STAT pathway see Frank, (1999), Mol. Med. 5:432:456 and Seidel et al., (2000), Oncogene 19:2645-2656.
JAK3 in particular has been implicated in a variety of biological processes. For example, the proliferation and survival of murine mast cells induced by IL-4 and IL-9 have been shown to be dependent on JAK3- and gamma chain-signaling (Suzuki et al., (2000), Blood 96:2172-2180). JAK3 also plays a crucial role in IgE receptor-mediated mast cell degranulation responses (Malaviya et al., (1999), Biochem. Biophys. Res. Commun. 257:807-813), and inhibition of JAK3 kinase has been shown to prevent type I hypersensitivity reactions, including anaphylaxis (Malaviya et al., (1999), J. Biol. Chem. 274:27028-27038). JAK3 inhibition has also been shown to result in immune suppression for allograft rejection (Kirken, (2001), Transpl. Proc. 33:3268-3270). JAK3 kinases have also been implicated in the mechanism involved in early and late stages of rheumatoid arthritis (Muller-Ladner et al., (2000), J. Immunal. 164:3894-3901); familial amyotrophic lateral sclerosis (Trieu et al., (2000), Biochem Biophys. Res. Commun. 267:22-25); leukemia (Sudbeck et al., (1999), Clin. Cancer Res. 5:1569-1582); mycosis fungoides, a form of T-cell lymphoma (Nielsen et al., (1997), Prac. Natl. Acad. Sci. USA 94:6764-6769); and abnormal cell growth (Yu et al., (1997), J. Immunol. 159:5206-5210; Catlett-Falcone et al., (1999), Immunity 10:105-115).
JAK1, JAK2, and TYK2 are expressed ubiquitously, whereas JAK3 is expressed predominantly in hematopoietic cells. The JAK kinases, including JAK3, are abundantly expressed in primary leukemic cells from children with acute lymphoblastic leukemia, the most common form of childhood cancer, and studies have correlated STAT activation in certain cells with signals regulating apoptosis (Demoulin et al., (1996), Mol. Cell. Biol. 16:4710-6; Jurlander et al., (1997), Blood. 89:4146-52; Kaneko et al., (1997), Clin. Exp. Immun. 109:185-193; and Nakamura et al., (1996), J. Biol. Chem. 271: 19483-8). They are also known to be important for lymphocyte differentiation, function and survival. JAK-3 in particular plays an essential role in the function of lymphocytes, macrophages, and mast cells. Given the importance of this JAK kinase, compounds which modulate the JAK pathway, including those selective for JAK3, can be useful for treating diseases or conditions where the function of lymphocytes, macrophages, or mast cells is involved (Kudlacz et al., (2004) Am. J. Transplant 4:51-57; Changelian (2003) Science 302:875-878). Conditions in which targeting of the JAK pathway or modulation of the JAK kinases, particularly JAK3, are contemplated to be therapeutically useful include, leukemia, lymphoma, transplant rejection (e.g., pancreas islet transplant rejection, bone marrow transplant applications (e.g., graft-versus-host disease), autoimmune diseases (e.g., diabetes, rheumatoid arthritis, lupus, psoriasis), and inflammation (e.g., asthma, allergic reactions). Conditions which can benefit from JAK3 inhibition are discussed in greater detail below. Recent data on JAK inhibition has been reported in kidney allograft patients treated with CP-690,550 and showed that markers of allogeneic response (interferon gamma) can be reduced (Van Gurp E A et al (2009) Transplantation 87:79-86).
Various groups have implicated JAK-STAT signaling in chondrocyte biology Li et al. (J Immunol. 2001. 166:3491-3498) showed that Oncostatin M induces MMP and TIMP3 gene expression in primary chondrocytes by activation of JAK/STAT and MAPK signaling pathways. Osaki et al (Biochem J. 2003. 369:103-115) showed that interferon-gamma mediated inhibition of collagen II in chondrocytes involves JAK/STAT signaling. Therefore, these observations suggest a role for JAK kinase activity in cartilage hemostasis and therapeutic opportunities for JAK kinase inhibition in Osteoarthritis. Additionally JAK family has been linked to cancers, in particular leukemias e.g. acute myeloid leukemia, acute lymphoblastic leukemia or solid tumors e.g. uterine leiomyosracoma and prostate cancer (e.g., Constantinescu, et al. Trends in Biochemical Sciences. 2007. 33(3):122-131). These results indicate inhibitors of JAK may also have utility in the treatment of cancers.
In view of the numerous conditions that are contemplated to benefit by treatment involving modulation of the JAK pathway it is immediately apparent that new compounds that modulate JAK pathways and methods of using these compounds should provide substantial therapeutic benefits to a wide variety of patients. Provided herein are novel compounds for use in the treatment of conditions in which targeting of the JAK pathway or inhibition of JAK kinases are therapeutically useful.
While progress has been made in this field, there remains a need in the art for compounds that inhibit JAK kinases, as well as for methods for treating conditions in a patient, such as rheumatoid arthritis, psoriasis, Crohn's disease, multiple sclerosis, asthma, acute myeloid leukemias (AML), solid tumors, and/or inflammation that can benefit from such inhibition. Moreover, the availability of compounds that selectively inhibit one of these kinases as compared to other kinases would also be desirable. The present invention satisfies this and other needs.